The field of the present invention is multispeed transmissions and controls therefor.
A wide variety of devices have long been available for mechanical engagement of rotating components. Where such engagement is to occur with the elements rotating, a variety of coupling mechanisms are frequently employed. In vehicle transmissions, clutches, fluid couplings, friction bands and synchronizing rings are typical. In many circumstances, these devices are quite adequate. However, many such devices are subject to power loss, rapid wear, lack of sufficient engaging strength and lack of sufficient engaging speed.
Mechanisms for automatically locking components have been employed which provide rapid engagement, very substantial engaging strength, and extended wear. One such device is a roller clutch which employs an engagement inner having an inner race, an engagement outer having an outer race and rollers therebetween. One of the two races has cam surfaces which are inclined relative to the other race. The rollers are set within a cage which generally rotates with the cam surfaces. A slight rotation of the cage relative to the cam surfaces results in selected engagement or disengagement of the inner and outer elements through wedging or releasing of the rollers. Such a roller clutch is disclosed in U.S. Pat. No. 3,283,611 to Weismann et al., entitled Positive Drive Differential. The disclosure of the Weismann et al. patent is incorporated herein by reference.
In the Weismann et al. patent, automatic disengagement of the mechanism occurs when differential speeds are experienced by the mechanism. However, employment of such a roller cam engagement mechanism with selective engagement and disengagement in transmission applications has alluded practical utility. The components exhibit substantially inelastic impact when coupling and, under certain circumstances, can experience repeated bouncing out of wedging engagement. Further, the engagement can be so rapid that damage might be done to other components in the rotating power train. Proper control of the cage such that it will remain properly oriented relative to the cam surfaces and yet remain selectively controllable for engagement and disengagement has also proven difficult.